Increasing evidence on the significance of nutrition in reproduction is emerging from both animal and human studies, suggesting a mutual association between nutrition and female fertility. Different “fertile” dietary patterns have been studied; however, in humans, conflicting results or weak correlations are often reported, probably because of the individual variations in genome, proteome, metabolome, and microbiome and the extent of exposure to different environmental conditions. In this scenario, “precision nutrition”, namely personalized dietary patterns based on deep phenotyping and on metabolomics, microbiome, and nutrigenetics of each case, might be more efficient for infertile patients than applying a generic nutritional approach. In this review, we report on new insights into the nutritional management of infertile patients, discussing the main nutrigenetic, nutrigenomic, and microbiomic aspects that should be investigated to achieve effective personalized nutritional interventions. Specifically, we will focus on the management of low-grade chronic inflammation, which is associated with several infertility-related diseases.

Background Type 2 diabetes is a chronic disease that has severe individual and societal consequences, which is forecast to worsen in the future. A new field of investigation is variations in circadian rhythm genes, in conjunction with diet and sleep variables, associations with, and effects on, type 2 diabetes development. Objective This systematic review aimed to analyse all current literature regarding circadian rhythm gene variations and type 2 diabetes, and explore their interplay with diet and sleep variables on type 2 diabetes outcomes. This review was registered with PROSPERO (CRD42021259682). Methodology Embase and Pubmed were searched on 6/8/2021/11/8/2021 for studies of all designs, including participants from both sexes, all ethnicities, ages, and geographic locations. Participants with risk alleles/genotypes were compared with the wildtype regarding type 2 diabetes outcomes. Studies risk of bias were scored according to the risk of bias in non-randomised studies – interventions/exposures criteria. Results In total, 31 studies were found (association n  =  29/intervention n  =  2) including >600,000 participants from various ethnicities, sexes, and ages. Variations in the melatonin receptor 1B, brain and muscle arnt-like 1 and period circadian regulator (PER) genes were consistently associated with type 2 diabetes outcomes. Conclusions Individuals with variations in melatonin receptor 1B, brain and muscle arnt-like 1 and PER may be at higher risk of type 2 diabetes. Further research is needed regarding other circadian rhythm genes. More longitudinal studies and randomised trials are required before clinical recommendations can be made.